Preterm refraction and ocular biometry in children with and without retinopathy of prematurity in the first year of life

The influence of variations in ocular biometric and optical parameters on differences in refractive error

PURPOSE

To present a paraxial method to estimate the influence of variations in ocular biometry on changes in refractive error (S) at a population level and apply this method to literature data.

METHODS

Error propagation was applied to two methods of eye modelling, referred to as the simple method and the matrix method. The simple method defines S as the difference between the axial power and the whole-eye power, while the matrix method uses more accurate ray transfer matrices. These methods were applied to literature data, containing the mean ocular biometry data from the SyntEyes model, as well as populations of premature infants with or without retinopathy, full-term infants, school children and healthy and diabetic adults.

RESULTS

Applying these equations to 1000 SyntEyes showed that changes in axial length provided the most important contribution to the variations in refractive error (57%-64%), followed by lens power/gradient index power (16%-31%) and the anterior corneal radius of curvature (10%-13%). All other components of the eye contributed <4%. For young children, the largest contributions were made by variations in axial length, lens and corneal power for the simple method (67%, 23% and 8%, respectively) and by variations in axial length, gradient lens power and anterior corneal curvature for the matrix method (55%, 21% and 14%, respectively). During myopisation, the influence of variations in axial length increased from 54.5% to 73.4%, while changes in corneal power decreased from 9.82% to 6.32%. Similarly, for the other data sets, the largest contribution was related to axial length.

CONCLUSIONS

This analysis confirms that the changes in ocular refraction were mostly associated with variations in axial length, lens and corneal power. The relative contributions of the latter two varied, depending on the particular population.

Corneal refractive error and astigmatism in patients aged 6 to 18 years with a history of retinopathy of prematurity and birth weight of <1500 g

PURPOSE

To investigate corneal refractive power (CR) and astigmatism (AS) in 6- to 18-year-old children with a history of retinopathy of prematurity (ROP) and birth weight of <1500 g who either did or did not undergo retinal photocoagulation (PC).

STUDY DESIGN

Retrospective study.

METHODS

We examined 143 eyes of 77 children in 2021. The children were divided into three groups for evaluation of CR and AS: those with a birth weight of ≥2500 g (normal birth weight [NBW] group, 13 eyes) as controls, those with spontaneously resolved ROP (sr-ROP group, 27 eyes), and those who underwent PC for treatment of ROP (PC-ROP group, 103 eyes). Swept-source anterior segment optical coherence tomography was used to analyze the cornea.

RESULTS

The median CR in the NBW, sr-ROP, and PC-ROP groups was 42.2 (41.3, 42.8) diopters (D), 44.5 (43.2, 45.5) D, and 45.2 (43.8, 46.6) D, respectively. The median AS in the NBW, sr-ROP, and PC-ROP groups was 1.2 (1.0, 1.5) D, 1.1 (0.8, 1.6) D, and 2.1 (1.4, 2.7) D. In the PC-ROP group, the with-the-rule astigmatic axis was 97%. In all three groups, a strong positive correlation was found between the mean anterior and posterior CR (NBW: r=0.795, sr-ROP: r=0.842, PC-ROP: r=0.890) and AS (NBW: r=0.883, sr-ROP: r=0.841, PC-ROP: r=0.860).

CONCLUSION

CR was significantly higher in the sr-ROP (p=0.013) and PC-ROP (p<0.001) groups than in the NBW group. The PC-ROP group had significantly more AS than the sr-ROP group. There was a strong correlation between the anterior and posterior CR and AS.

Refractive Status and Biometric Characteristics of Children With Familial Exudative Vitreoretinopathy

Purpose

To compare biometric characteristics between patients with early-stage familial exudative vitreoretinopathy (FEVR) and healthy controls.

Methods

This case-control study included 50 FEVR eyes in stage 1-2 and 50 control eyes matched by age, gender and spherical equivalent (SE). Biometric parameters including axial length (AL), white-to-white diameter (WTW), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), pupil diameter, vitreous chamber depth, anterior and posterior corneal surface curvature radius (ACR and PCR), anterior lens surface curvature radius (ALR) and posterior lens surface curvature radius were measured using IOLMaster 700 and compared between cases and controls using paired t-test. Correlations between SE and biometric measures were assessed using Pearson correlation coefficient (r) in cases and controls.

Results

Both FEVR cases and matched controls had a mean age of 7.6 years, 48% female and mean SE of -5.3 D (80% myopia). Compared to controls, FEVR eyes had smaller AL (P = 0.009), WTW (P = 0.001), ACD (P < 0.001), and ALR (P = 0.03), but larger CCT (P = 0.02) and LT (P = 0.01). In FEVR eyes, SE was negatively correlated with AL (r = -0.79, P < 0.001), positively correlated with ACR (r = 0.29, P = 0.04) and PCR (r = 0.33, P = 0.02), whereas in controls, SE was negatively correlated with AL (r = -0.82, P < 0.001) and LT (r = -0.34, P = 0.02), positively correlated with ALR (r = 0.29, P = 0.04).

Conclusions

Patients at early stage of FEVR exhibited a unique eye morphology resembling ocular development arrest, which may help to develop screening and early detection tools for FEVR. In FEVR patients, myopia is very prevalent and significantly associated with corneal curvature increase.

Longitudinal Change of Refractive Error in Retinopathy of Prematurity Treated With Intravitreal Bevacizumab or Laser Photocoagulation

PURPOSE

To compare progression of myopia and refractive error in former premature infants with retinopathy of prematurity (ROP) treated using intravitreal bevacizumab (IVB) or laser.

DESIGN

Retrospective clinical cohort study.

METHODS

We identified premature infants with ROP treated using IVB from 2011 to 2020 and compared their longitudinal cycloplegic refraction data to that of infants with ROP treated using laser during the same timeframe. A subset of infants treated using IVB also underwent additional treatment using laser. We included cycloplegic refractions from 789 cumulative visits over a median 3.2 years. We used a linear mixed-effects model with a log decay function to evaluate how refraction changed with age after treatment.

RESULTS

In aggregate, the model estimated a significant (P < .001) trend in refraction-from slight hyperopia to relatively more myopic states. However, progression in laser-treated eyes was significantly (P < .001) more rapid, regardless of treatment with IVB. The number of laser spots resulted in increased myopic progression by approximately 0.16 diopters per 100 laser spots. Both ROP stage and zone had a significant effect on myopic progression, with more severe disease resulting in faster myopic progression. Random effects, including individual subject variation with nested variance for left and right eye, accounted for 86.4% of the remaining variance not explained by age and treatment.

CONCLUSIONS

Laser treatment for severe ROP increases the trend to severe myopia. In our sample, IVB did not affect myopic progression but did substantially reduce the amount of consequent laser required to treat ROP. The effect of laser persists after accounting for differences in ROP stage and zone.